![]() ![]() Researchers have since searched for ways to deliver gene therapy without such side effects. In the early 2000s, gene therapy trials for SCID-X1 were temporarily halted after several patients developed cancer. Importantly, she said, patients did not require ongoing treatment, as is often required with other therapies, and no patients had developed leukaemia - a side effect of previous trials. "The outcomes have been truly outstanding for our patients," Dr Mamcarz said. Within three months of treatment, T cells and NK cells (immune cells that help fight infections) and B cells (which produce antibodies) were present in the blood of all but one baby, who required a second dose of gene therapy. "Prior to the gene-corrected blood stem cells being infused back into patients, the infants received two days of low-dose busulfan - a chemotherapy agent commonly used in bone marrow transplantation to make space in the marrow for donor stem cells to grow," Dr Mamcarz said.Īfter 10 days, the cells were returned to the babies' body, with a virus carrying the corrected gene, where they were able to proliferate and produce healthy immune cells. Using this process in the SCID-X1 trial, doctors removed the babies' bone marrow to harvest stem cells, which were frozen, tested, and infected with a virus carrying a working copy of the defective gene. Viruses are often used as vectors because they're good infecting and sticking DNA into cells.įor gene therapy, the infectious part of the virus is removed, and the healthy gene hitches a ride as the virus enters the cell, without making the patient sick.ĭavid Vetter, a child born in 1971 with SCID, became famous for living in a sterile environment. To add a healthy copy of a gene into a person's genome, scientists use what's known as a vector. The idea of gene therapy is to introduce, remove or change the genetic material in cells to treat a specific disease.įor example, a bad gene may be replaced with one that is healthy, a new gene might be added to perform the function a gene that is defective or missing, or a problem gene might be switched off. If a person is born with a defective, missing or mutated gene, they can develop a disease. Genes, made up of DNA, are our body's blueprint.Įach human cell has about 25,000 genes, and each gene's DNA sequence contains instructions on how to build certain enzymes and proteins, each of which has a specific job. The rest must rely on a stem cell transplant from another donor, which is not always possible, and when it is, is less likely to cure SCID-X1 and more likely to lead to severe complications. But only one-fifth of babies have such donors. ![]() Until now, the best treatment for SCID-X1 has been a stem cell transplant from a tissue-matched sibling donor. a first for patients with SCID-X1," Dr Mamcarz said. "These patients are toddlers now, who are responding to vaccinations and have immune systems to make all immune cells they need for protection. Within months of treatment, all 10 children produced functional immune cells for the first time, said Ewelina Mamcarz, a paediatric haematologist-oncologist at St Jude Children's Research Hospital and co-author of the study published in the New England Journal of Medicine on Thursday. In a study of eight children diagnosed with SCID-X1, doctors collected patients' bone marrow and inserted a corrected copy of their mutated gene (the one that caused them to have little immunity) into the DNA of their blood stem cells. Only boys are affected, due to the faulty gene's pattern of inheritance. The disorder, which is estimated to affect about one in 100,000 newborns, is caused by a mutation in the gene that produces a protein essential for normal immune function. A simple infection like a common cold can be fatal. If left untreated, patients with SCID-X1 - the most common type of SCID - rarely live past their first birthday. Researchers now hope treatment will provide a template to develop new gene therapiesĬhildren with the disorder, called severe combined immunodeficiency or SCID, are born without a functional immune system, meaning they have little to no way of protecting themselves against infection.ĭecades ago, patients with SCID had to be kept inside special plastic chambers, which led to a public fascination with the disease and several 'bubble boy' Hollywood films.Doctors extracted the patients' bone marrow and corrected the genetic defect in their DNA.The babies, born with little virtually no immune protection, now have fully functional immune systems.Infants born with an extremely rare, life-threatening genetic disorder sometimes known as 'bubble boy' disease have been effectively cured thanks to a gene therapy developed by US scientists. ![]()
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